Preparation of wood for pulp manufacture



?atenietl Nov. .3, 1%25.

JOSEPH BI. WALLACE, 0F STAMFORD, CONNECTICUT. ASSIGNGE TO PINE WASTE PROD- UCTS, INQ, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE.

YEEPAQATION OF FOOD FOR PULP ZJIANUFAC'IURE.

Ho Drawing.

To ail whom it may concern:

Be it known that I, Josnrn H. WALLAC a citizen of the United States, and a resident of Stamford, county of Foirfield, and State of Connecticut, have inverted c rtain new and useful Improvements in Preparation of Wood for Pulp lilanulacture, of which the following is a specification.

This invention relates to the treatment of wood, and particularly southern pine in preparation for the manufacture of pulp and for the recovery of high grade products therefrom.

The main objects of the invention, are twofold, first, to reduce the wood to a size and condition best. suited for the manufacture of, commercial paper pulp, and second, in the course of such treatment to recover valuable products carried by the Wood.

At the present time one of the most available sonrces of wood for pulp purposes is the yellow pine of our southern forests, including what is known as the long and the short leaf, Cuban and loblolly. Other available sources are the balsams, the various tamaracks and Douglas fir. These pines, as well known, possess long grained fibres of a superior character for paper making and also carry a large proportion of valuable turpentine and resinous compounds. This high content of turpentine and resin has made the treatment of these woods for pulp purposes particularly difficult. In the alkali procesv ts, too much ot'tlie alkali is consumed by combination n'iththe resins; and the digestcr liquor is cumbered with great amounts of resins and resin soaps. The paper maker wants some resin present, but n t .too much; and he does not desire highly acid resins. Further, the material is irregular as regards its eon'iposition, some chips bcin' highly resinous while others are not, which renders operation irregular. For these reasons the pines mentioned, in spite of their high grade fiber, have not been much used.

In the present invention, I obviate these diilicultics by submitting the wood to what may be called a partial extraction treatment, removing some but not all of the resins and t-erpenes. I aim to take out a substantial quantity of the total extractable matter, while leaving a substantial quantity behind. From the paper Inakers standpoint this has Serial No. 495,964.

the advantage of providing an open textured, per 'ious chip containing some, but not much resin and having the resin therein substantially uniformly distributed; while it has further very great, advantages,from the view point of the quality. of the extracted matter.

' Southern pine contains many and varied substances o l the general nature of terpenes and resins; and it is common to submit it to extraction to regain these, Many methods have been proposed, and many hundreds of patents dealing with this problem have been issued. Most oit' these treat finely divided wood with some solvent such as gasolene, henzol, benzine, naphtha, etc; others suggest a mild treatment with solutions of alkalies to saponii'y the resin and render it watersoluble without attacking the remainder of the wood. Solvent methods have advanced the farthest along the road toward successful commercial exploitation, but none of these has yet attained complete success. This is for various reasons, one being that the effort is to do too much; to get as great a quantity of extractive as possible. The wood is comminuted in order to aid extraction; and this ruins the residue for the paper making process. Another is that in securing a large total yield of extractive, the quality of the product is low.

The highest grade rosin or colophony made is procured from clean gum turpentine. The pine wood itself contains this same material; but it also contains very many other things; and with any long continued and exhaustive extraction, thesiother things are also extracted and reduce the grade of rosin procured very much.

l have found that if the wood be extracted with a solvent, the operation really takes place in two phases; a li st stage where natural solvent.

lion is wanted. to secure the two extracts separately. If however chips for paper making are wanted. it is better to confine the operation to the one stage, leaving residual resins and terpenes in the wood for the plup mill to deal with. As stated. the presence of a certain amount of these bodies is desirable for pulp mill purposes in any event.

In the practice ofmy invention the co niferous wood is reduced to pulp mill size, that is long fibred chips of a size best answering the requirements of the paper manufacturer. These mill size chips may average from ,4 to of an inch. in length, to 1% inches in width andl/ to inches in thickness.

These long fibred mill size chips are charged vinto what I have termed an; extractor*and there treated with a solvent preferably like the natural solvent disclosed by Clopo Patent No. 1,144,171 June 22, 1915. As an object of the present invention is to obtain high grade extractives by a partial extraction, this solvent is here particularly useful as it imparts nothing foreign to the extract. This solvent may be applied either in the form of a liquid or vapor. At the present time, I prefer to use the liquid and in a moderately heated condition. This liquid is caused to percolate or circulate through and around the body of chips and in its passage it extracts the resin, turpentine, pine oil and also a fresh supply of the These products are suitably collected and separated, usually by disillation, in which case, the turpentine passes oil at and around 160 degrees 0., the solvent between about 160 and 180 degrees C., and the pine oil at and above approximately 180 degrees C., leaving the rosin as a residue.

This treatment is not continued, as in Clope, to the point where a substantially complete extraction is effected,- but on the contrary it is discontinued after the point of maximum elliciency is reached. This point may be determined by tests, and depends upon a number of different factors. The extraction is more rapid at the beginning, tapering oil in volume as the operation proceeds, and at the point where it is no longer economically profitable the operation is discontinued. In dilferent runs which I have made the extraction has been carried on for periods ranging from about to 2 hours as againstd. to (3 hours needed for the usual process.

A convenient method of determining the extraction period is to plot extraction curves showing the rate of extraction in intervals of time. These curves show a rapid extraction for the first short interval of time, and an abrupt change in the direction of the curve at the end of this first extraction pe riod. The approximate location of the commeroially etiioient point for the discontinib ance of the extraction is therefore indicated by this relatively abrupt change in the extraction curve. This point will vary moderatelyhowever, with changes in the market value of the products and labor charges and other elements entering into the cost of production. For instance, at a time when lur pentine and rosin have a high market value.

the commercially ellicient period of treatment will be longer than at a time when these products are at low market value. It is a commercial question between more and lower grade extract and less cxtriu-t of higher grade. In all events, however. the extraction is continued to a point where the chips are free of the turpentine and resinous constituents to such an extent that they ma be economically handled in the usual paper making processes. Ordinarily this point is reached where about 30 per cent of the total extractable matter is left.

At the end of the extraction treatment, steam or other agent may be passed through the'chips to clear them of the free solvent.

The apparatus necessary for the partial extraction described. is relatively simple and may be made in portable form so that it is possible to carry out this new process in the woods, or in other words at the source. .\'0 chemicals are required other than the natural solvent. and this as abovedescribed, is produced as needed at the field plant.

After treatment nothing is leftwith the cellulose but those materials which are readilv removed by the 'pulping process. The chips are in a porous condition and therefore easily reduced to pulp, and what is quite important to thepaper manufacturer. have a substantially uniform and constant moisture content. This enables the pulp maker to deal with the chips. with greater certainty and less experimentation than has been possible heretofore where the moisture content varies greatly.

The suspension of the extraction treatment after the removal of that portion of the resinous and other materials which can be obtained with the minimum of time and etfort and the maximum of efficiency, keeps the cost of extraction at a commercially two nomical point, and furthermore, results in the production of superior grades of the resin and other constituents. This is because superior products are extracted during the early part of the treatment, that is in the period of maximum extraction elliciency. I attribute this partly to the fact that the natural resins occurring in the pine in time undergo oxidation and other injurious transformations subsequent to their formation in the tree, which transformation products are inferior to the virgin gum. This is particularly true of the resins in stumps and dead trees, or in other words, lightwood, a material which is most available for solvent treatment. readily acted upon by the natural solvent, and a short treatment therewith, results in the removal of a lesser amount of the same.

Another important oint of my invention arises, from the fact t iat any long exposure of the resins, especially ro in, to heat and to contact with metals, particularly iron, produces decomposition resulting in diminution in the value of the resins. The reduced ex traction of my invention involves a substantially lessened exposure of the resin to heat and contact, with the metal of the apparatus so that the resin produced is for this reason also of a superior quality.

From the foregoing, it will be seen that my invention furnishes to the pulp manufacturer a long tibred mill size chip ready for the pulping process and which is porous and has a substantially standardized moistur and resin content. and therefore, best Fullills requirements of pulp making. Furthcrumrc. the preparatory work on these w ran be commercially and imixpensivcly ri i'l out directly at the source. It is also apparent that the process is an eermomical one, on::ncrcially practicable, and that by an obtained high grade extraction pro-torts.

ll stopping the extraction process at the point of maximum efliciency or eonuncrcial economy, the by-products can be made to pay for the chips. and the chips freed of the greater part of the turpentine and resinon constituents provide a sut erior material for pulp purposes. All the operations described may be readily carried on in the woods. at... the apparatus necessary is not calpeti ivc. or complicated or cumbersome bethe operations are carried on at low -urc mat low temperature. The dison. for the separation of the more volats from the resin may be car-- it the held or any convenient pram. lilL :11 any rate, the resin is usually 1 hired at the tichl plant.

im the other hand. if the partially extract- Hi; s we to be hippe l some distance the m- 'y llllcttt may be reduced by a suitihyu; process to approximately 12 to 1.1 per cent so that the chips will not give ..p n1 tmlte on moisture in transit and will h i 'cittktl at the paper mill with a .-turc content. and can he treated P "the pat lly extract d chips are subject- Ml t a liking" process the pulp mill reduce them :o the cellu ose condition m-w sary tor pulp uianu are. lsually c :m'ompli he l by disintegrating chips -z ltt' means of hot solution of 1 l :h as iaustic alkali or acid .surh turpen ine and other volatile utmnot removed in the partial :rt-atmcnt oi the chips may be terpen es extraction These inferior resins are less-- recovered, in a large measure, in this latter stage of the operations from the waste gases of the digester.

In an application. Serial No. 405,963, filed herewith, I have described and claimed a process'similar to that disclosed herein for recovering extracts from resinous Woods, and in another application, Serial No. 405,965, also tiled herewith, I am claiming such ulp mill chips as may be made by means oFthe present invention.

What I claim is:

1. The process of producing long-fibred relatively porous pulp mill chips having materially less resinous matter than that normal to the wood, said resinous matter being distributed substantially uniformly therethrough, which comprises reducing resinous coniferous wood to pulp mill-size chips, subjecting the same to a solvent throughout that period where the action of the solvent is most rapid and the rate of extraction is highest, and discontinuing such extractive treatment at or about the point where there is an abrupt reduction in the rate of extraction of matters soluble in said solvent and while there yetremains in said chips a substantial amount of matters soluble in said solvent,

2. The process of roducing a material for pulp mills whic comprises treating resinous coniferous pulp mill chips with a solvent throughout that period where the solvent is most active and the rate of extraction is highest, and discontinuing such extractive treatment at or about the time the rate of extraction is abruptly reduced and while there yet remains in said chips a substantial amount of matters soluble in said solvent.

3. The process of treating resinous coniferous wood to remove the extractives of greater value and to leave the wood in open porous texture with a substantial quantity of resinous matter less than that no al to the wood distributed substantially uniformly therethrough, which comprises subjecting the wood to the action of a hot solvent throughout a period of time which is rela tively short as compared to that necessary for complete extraction of the wood by said solvent and discontinuing such extractive treatment substantially at the end of the period where the extraction rate is highest and substantially at that point where only the lighter extra'ctives have been removed; said wood still retaining a substantial amount of matters soluble in said solvent.

4. The herein disclosed process which comprises only partially extracting pulp mill chips with a solvent and then subject iutz said partially extracted, chips to a pulp lag treatment in whjch the residue of the eve tracti in the partially extracted chips is removed,

The heurin disciosvd pmcess which pulping treatment of such volatile terpanes (:mnpzisera flniy part' iXiltHti'flg pulp as were not, cxn'avted during the first operamiil chips with a SUER'U! 4 and than subjecv tinn above. 10 ihg mid partiniiy vxmar-fwi vhips in a pulp In Witflfifis wh rmf, I have hercunm set 'mg trentz'nm in bid! he rweidmn5 he 9X" my ham? his 123d day of August, 1920. trmtiw in thvv paminll v erhacvfi (M is I'ammm, imlwling iha XBF-fH'iizEj during sm-h JOSEPH H. WALLACE. 

